My bad, you're right, the actual diff is different, but from what I recall, it is geared the same as the j30. I also always thought that it could be made to work, you just had to swap the pumpkins Maybe I'm getting my cars mixed up.

the NA z32 diff is geared at 4.08, which, as I remember it, is the same as the stock 240 diff, and in this case, the same as the s14 vlsd diff.
The NA z32 diff might actually be cheaper/easier to get a hold of than a s14 diff. Hell, I've got two sitting in my garage.

The J30 diff is geared at 3.9, which I thought was the same as the TT diff. I honestly don't remember. I've always just planned of swapping in a TT engine into my NA shell.